Present methods of motion and occupancy detection which utilize active microwave, infrared/optical, and acoustic/ultrasonic motion apparatus operate by transmitting an electromagnetic or acoustic wave into a region of interest, via one or more transmitters, which then reflect off of objects in the region of interest and are detected by one or more receivers. A Doppler shift of the reflected signals indicates the presence of movement within the region of interest.
Typical applications of motion and occupancy detection are described in U.S. Pat. Nos. 4,661,720, 5,189,393 and 5,640,143.